1. Field of the Invention
This invention relates to surface active agents, and more particularly, to surface active agents which are useful in dispersing particles in aqueous media or in a media of water and an organic solvent which is a nonsolvent for the particles.
2. Description of the Prior Art
The dispersion of particles in a liquid media, which is a nonsolvent for the particles, typically involves the utilization of a surface active agent. These surface active agents are disposed at the surface of the particles by chemical groups which have an affinity for the particle surface on one end of the molecule and an affinity for the dispersing media at the opposing end of the molecule. Thus, when the particles are sufficiently small in size, a stable homogeneous suspension or dispersion of the particles is produced.
This principle has applications in a plurality of fields wherein solid particles and liquids are to be dispersed in a nonsolvent media. Typical of these fields are paint compositions, insecticides, fungicides, herbicides, ink compositions, emulsion polymers and the like. More particularly, these surface active agents have found use in dispersing dyes and pigments in solvent or aqueous media for dyeing textile fibers, leathers or the like.
In dispersing these dyes, pigments and other particulate solids, it is necessary to reduce the particle size of the solids to 2 microns or less in order that a stable homogeneous dispersion of the particles be formed in the media. Additionally, a sufficient amount of surfactant must be included in the grinding process, i.e. particle reduction, in order to dispose the surface active agent at the surface of the particles for appropriate association therewith to impart stability to such dispersion.
In a typical process for dispersing pigments and dyes, the particulate solids dispersed in a liquid nonsolvent medium are continuously passed through a mill in order that the appropriate particle size be obtained for subsequent utilization in a dyeing process or the like. Subsequent to obtaining the appropriate particle size the dispersion may be dried to 100 percent solids and then redispersed or used in a dyeing process directly. These processes require a great deal of energy consumption for grinding and high concentrations and quantities of dispersing agents, i.e. surface active agents, in order to grind the particles to the appropriate size.
Commercial dye preparations comprise dye or pigment cake, that is, a dye compound which generally contains minor amounts of impurities, a water soluble diluent for standardization purposes such as sodium sulfate, and one or more water soluble surfactants. Due to reactant impurity or the nature of the multistep reactions used in the synthesis of the dye compounds, the color yield or shade from different batches of the dye cake will vary. The dye preparation must therefore be standardized by varying the amount of dye and diluent used in the dye preparation so that the color or strength of the preparation is the equivalent of a sample used as the standard.
Further, in the dyeing process it is necessary to obtain a disperse dye having a particle size of less than 2 microns, and preferably, in the range of 0.3 to about 1.5 microns to obtain a dyed article which is "level." Again, the grinding process to obtain the desired particle size is critical in conjunction with the surface active agent in order to obtain the homogeneous dispersion and level dyeing.
Several surface active agents have been utilized in connection with disperse dyes, pigments and the like solid particulates which are dispersed in a liquid media. Typical surface active agents are lignin sulfonates, sorbitan, fatty acid esters, fatty acid esters of sodium sulfosuccinate, alkane sulfonates, ethoxylated alkylphenols and their sulfonates, ethoxylated amines, amides and their sulfonates and the like.
A great deal of success has been achieved utilizing lignin sulfonates in dispersing dyes. However, even with the lignin sulfonates, high levels of surface active agent and severe grinding conditions are required in order to obtain an acceptable disperse dye. Typically, 60 to 70 parts by weight of a dispersing agent such as sodium lignin sulfonate per 100 parts by weight of the commercial dried disperse dye are required to obtain an acceptable composition. In accordance with the present invention, a surface active agent is provided which is useful in dispersing solids and liquids in a liquid nonsolvent. More particularly, in accordance with the present invention, a surface active agent is provided for dispersing dyes and pigments which can be utilized at a much lower level than that known in the prior art while achieving comparable, if not superior, results.